An experimental study of Ion Acoustic (IA) wave propagation is performed to investigate the effect of neutral density for argon plasma in an unmagnetized linear plasma device. The neutral density is varied by changing the neutral pressure, which in turn allows the change in ion-neutral, and electron-neutral collision mean free path. The collisions of plasma species with neutrals are found to modify the IA wave characteristics such as the wave amplitude, velocity, and propagation length. Unlike the earlier reported work where neutrals tend to heavily damp IA wave in the frequency regime (where is ion-acoustic mode frequency and is ion-neutral collision frequency), the experimental study of IA wave presented in this paper suggests that the collisions support the wave to propagate for longer distances as the neutral pressure increases. A simple analytical model is shown to qualitatively support the experimental findings.

The Infrared Imaging Video Bolometer (IRVB) is one of the modern plasma imaging diagnostics which provides the measurement of the temporally as well as spatially resolved (2-D/3-D) power profile radiated from plasma devices. The technique has successfully been tested on a large size tokamak (JT-60U) and the same technique is for the first time being utilized for the medium size tokamak ADITYA (R = 75 cm, a = 25 cm, I p = 80 kA, T e (0) ∼ 350 eV, N e ∼ 1.5 × 10 13 cm 3 , B T = 0.7 T), where the plasma shot duration is ∼ 100 ms and radiated power brightness level is ∼ 2 W/cm 2 . The diagnostic is utilizing a 6.4 cm × 6.4 cm size and 2.5 µm thick, free standing Platinum foil. A square aperture 0.7 × 0.7 cm 2 of pinhole camera geometry can provide 9 × 9 bolometer pixel arrays (81 channels) and ∼ 7 cm of spatial resolution at plasma mid-plane with a 45• × 45• wide field of view. This wide field of view covers two semi-tangential views, on either side of the radial view in the tokamak along with a poloidal view. A medium wave infrared camera having 320 × 240 focal plane array, 200 Hz frame rate, noise equivalent temperature difference ∼ 20 mK is used and 10 ms of optimal temporal resolution is experimentally achieved. The present paper discusses the design, development and calibration of the system. The performance of the IRVB system for its time response is experimentally investigated and has also been reported here.

This article presents the experimental observations and characterization of ion acoustic solitons (IASs) in a unique multi-pole line cusp plasma device (MPD), in which the magnitude of the pole-cusp magnetic field can be varied. In addition, by varying the magnitude of the pole-cusp magnetic field, the proportion of the two-electron-temperature components in the filament-produced plasmas of the MPD can be varied. The solitons are experimentally characterized by measuring their amplitude-width relation and Mach numbers. The nature of the solitons is further established by making two counter-propagating solitons interact with each other. Later, the effect of the two-temperature electron population on soliton amplitude and width is studied by varying the magnitude of the pole cusp-magnetic field. It has been observed that different proportions of two-electron-temperature significantly influence the propagation of IASs. The amplitude of the solitons has been found to be inversely proportional to the effective electron temperature (Teff).

This paper describes an objective scheme to estimate wind speed from the available isogonal field in the interior region and wind speed and direction for the boundary region. As a first step, the mean monthly wind field is taken as a guess field for the interior region. The divergence field is then computed, which along with the wind direction for the interior region is used to improve the guess field in successive scans, so as to match it with a the wind field along the boundary. This method has been tested over central India, a region of good conventional network. The results of the scheme which has potential advantages for augmenting data in otherwise sparse data region, is discussed.